This project compares the selective gating of cations by a synthetic phospholipid membrane with the cation relationships of Na K ATPase. The membrane selectively conducts K ion and ions of nearly the same size, and its conduction is stopped by AG ion, Hg ions, Zn ions, Ca ions and many amines. Similarly the Na-K-ATPase requirement of K ion can be satisfied by those ions which conduct in the synthetic membrane, and the enzyme is inhibited by those ions which stop that conduction. The effects of the same ions on dephosphorylation of Na-K-ATPase parallels the effects on the overall enzyme activity. In this period the effect of ions on the partial reaction of Na-K-ATPase will be studied further. One of the relationships between ions have suggested the possibility of defining one of the phosphorylation intermediates, and this possibility will be pursued.